1. Field of the Invention
This invention relates to apparatus for magnetically recording data on disks including flexible disk assemblies generally known as diskettes. More particularly, this invention relates to such recording utilizing magnetic head assemblies having a tunnel erasing function through the expedient of erasing transducers positioned on the active face of the magnetic recording head on opposite sides of a central read/write transducer.
2. Description of Prior Art
Magnetic recording systems utilizing magnetic heads to record and reproduce information from serial storage magnetic media has been of increasing importance over the past 20 years. The criticality of improving the magnetic characteristics of such heads has become more pronounced since the magnetic recording technology is constantly attempting to improve the area density of information recorded and reproduced on such magnetic media. Accordingly, the industry is constantly attempting to improve track density, i.e., increasing the number of tracks per inch across the recording surface of the magnetic medium. For example, magnetic media recording systems have advanced from original magnetic tapes and cards wherein the information was magnetically recorded in rectilinear tracks at a density in the order of 25 tracks per inch to the present more advanced magnetic disks including flexible diskettes wherein information is recorded in curvilinear tracks in densities varying from 48 to 500 tracks per square inch.
The track density is dependent upon the width of a track of information and thus requires minimizing the effect of width of the transducing gap of a magnetic transducer. One method of reduction is to utilize a read/write transducer having a relatively large gap width and to provide erase means for erasing the edges of the written track immediately after it is written. This expedient is known as tunnel erase or trim erase. In this manner, a narrow track of information will be effectively written and additionally, a wider track may be read by the transducer during the read mode through the deactivation of the erase means.
The status of this tunnel erase magnetic recording technology is comprehensively set forth in U.S. Pat. Nos. 3,769,469, Garnier et al and 4,110,804, Castrodale et al, both assigned to the assignee of the present invention. The apparatus of these patents which is directed towards high density recording on magnetic disks including flexible diskettes comprises a magnetic head recording assembly under which the curvilinear tracks of said disks rotate. The assembly comprises a central read/write transducer which essentially is a magnetic core with a gap on the active face of the head assembly and with a read/write coil wound on the magnetic core; and a pair of additional transducers which are in effect magnetic cores on opposite sides of the central magnetic core forming a pair of erase gaps on the active face of the head assembly. These erase cores of course contain coils which may be a pair of coils, one for each core or a single coil connected across both erase cores.
With this greatly expanded storage capacity for magnetically recorded information in disks, problems have arisen with respect to the preservation or safeguarding of the stored information against destruction or loss due to unexpected or random conditions which may cause unplanned activation of the recording assembly. For example, simple diskette memories at the present time can contain in the order of one million bytes of data which is the equivalent of about 500 printed pages. Thus, loss through the random overwriting or erasure of data can be very substantial and damaging to the user. This is particularly the case when the erased or overwritten tracks are indexing tracks on the disk memory since without indexing tracks, access to other data on tracks which are not destroyed becomes impossible.
Accordingly, there is a need in the disk recording art for effective apparatus for safeguarding data on the disk from such random destruction. As will be hereinafter set forth, the present invention provides such an expedient which is both simple to implement and effective to use. The present invention involves the monitoring of current in both the read/write transducers and the associated tunnel erase transducers in order to determine whether there is any unwarranted random activation of such transducers.
U.S. Pat. No. 3,434,156 discloses an expedient of monitoring the current during an activated write operation on magnetic media involving magnetic transducer heads. However, the apparatus of this patent appears to be directed solely to the determination of whether the preselected write operation is functioning properly. The teaching of this patent does not deal with the problem of safeguarding against lost recorded information and therefore is not concerned with the monitoring or sensing of unwarranted activation of the write function let alone the unwarranted activation of a tunnel erase function. U.S. Pat. No. 4,149,241 is representative of a group of patents which teach current monitoring in general. In this particular application, a communications buss monitor is described. The patent does not deal with magnetic media recording or safeguarding against inadvertent write or erase operations.